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  Disposable chamber for analyzing biologic fluidsUSPTO Application #: 20070243117Title: Disposable chamber for analyzing biologic fluids Abstract: An apparatus for analyzing biologic fluid is provided that includes a first planar member, a second planar member, and at least three separators. At least one of planar members is transparent. The separators are disposed between the members, and separate the members to form a chamber having a height. At least one of the members or separators is sufficiently flexible to permit the chamber height to approximate the mean size of the separators. During use, the biologic fluid to be analyzed is disposed within the chamber. (end of abstract)
Agent: O'shea, Getz & Kosakowski, P.C. - Springfield, MA, US Inventor: Stephen C. Wardlaw USPTO Applicaton #: 20070243117 - Class: 422255000 (USPTO) Related Patent Categories: Chemical Apparatus And Process Disinfecting, Deodorizing, Preserving, Or Sterilizing, Physical Type Apparatus, Means Separating Or Dissolving A Material Constituent The Patent Description & Claims data below is from USPTO Patent Application 20070243117. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Technical Field [0002] The present invention relates to chambers for analyzing biologic fluids in general, and to chambers that permit the enumeration of particulate matter within the biologic fluid in particular. [0003] 2. Background Information [0004] The classic method of enumerating particles in a liquid medium, such as blood cells in whole blood or bacteria or other material in urine or other biologic fluid is the hemocytometer, which includes a chamber manufactured to a precise height and having visible ruled areas of precise dimension. The liquid containing the particles to be enumerated is introduced into the chamber. The liquid is diluted if necessary to reduce the number of particles to a manageable number. The operator then counts the number of particles in a given demarcated area. Since the area and height of the chamber are precisely known, the particle count per volume can be calculated. Although these chambers are generally ruled to demarcate a known area, this is not necessary if such a chamber is used in an image analyzer. With an image analyzer, rulings on the chamber itself are unnecessary because the field of view can be exactly calculated from the image. [0005] Because they are precisely manufactured, hemocytometer chambers are relatively expensive and were not considered disposable. Modern precision plastics molding techniques have allowed the manufacture of some types of hemocytometer chambers at sufficiently low cost so as to be considered disposable in some instances, but chambers requiring substantial precision and/or thicknesses less than the traditional 0.1 mm are very difficult to mold accurately. [0006] U.S. Pat. No. 4,950,455 describes a counting chamber formed from a rigid glass slide and a rigid glass coverslip with rigid particles, such as glass beads, contained therebetween. The beads maintain a thin spacing between the slide and coverslip, thereby forming the counting chamber. [0007] A counting chamber formed from rigid upper and lower panels separated by rigid particles has substantial limitations, however. Referring to FIGS. 1 and 2, a prior art assembly generally denoted by 2 consists of a lower glass slide 3, an upper glass coverslip 4 and an entrapped layer formed from a plurality of glass beads 5. Because any microscopic beads are not completely uniform, having a coefficient of variation of the diameter of up to 10% or greater, the larger beads 6 "prop-up" the coverslip 4 to some extent, and the smaller beads 7 have no effect on the separation. The differences in bead diameter is a problem because while it is easy to determine and/or control the mean diameter of the beads, the spread of diameters is less well controlled, rendering the system less accurate than is desired. This results in a separation between the upper and lower layers of about the mean bead diameter plus one standard deviation. A greater problem is the presence of particulate debris as shown in FIG. 2. This debris can be present when the chamber is made or can be introduced by the environment or from a sample. The debris 8 can "prop up" the coverslip 4 and create a large area of increased volume in the chamber, which destroys its accuracy. [0008] Another issue with this type of prior art chamber is that it is difficult to package a plurality of such disposables in an instrument used for automatically scanning and counting particles, such as an image analyzing system. [0009] What is needed is an apparatus and method to overcome the limitations of the prior art, that provides a chamber for analyzing biologic fluids, including the enumeration of particulates within the fluid, which is inexpensive to produce, relatively insensitive to trapped particulate debris, and amenable to packaging for use in an automated test system. SUMMARY OF THE INVENTION [0010] According to the present invention, an apparatus for analyzing biologic fluid is provided that includes a first planar member, a second planar member, and at least three separators. At least one of planar members is transparent. The separators are disposed between the members, and separate the members to form a chamber having a height. At least one of the members or separators is sufficiently flexible to permit the chamber height to approximate the mean size of the separators. During use, the biologic fluid to be analyzed is disposed within the chamber. [0011] According to one aspect of the present invention, each planar member is a tape that can be wound on a reel. In some embodiments, the planar members are initially attached to one another. In other embodiments, each planar member is initially separated from the other planar member. [0012] According to one aspect of the present invention, a cassette is provided having at least one source reel and at least one take-up reel. The planar members are initially wound on a source reel, and are transferred to a take-up reel during operation of the apparatus. An analysis region is disposed between the source and take-up reels. The planar members pass through the analysis region during the operation of the apparatus. [0013] There are numerous advantages associated the present invention. We discovered that if a counting chamber is produced using separators disposed between planar members, and if at least one the planar members and separators is flexible, the chamber behaves differently than the prior art devices, and the difference is highly advantageous. When a counting chamber is filled with a liquid, the capillary forces tend to pull the top and bottom planar members together, thus exerting a slight pressure on the retained separators. This pressure will cause the flexible element to deform in such a manner as to cause the chamber thickness to approximate, on average, the mean dimension of the separators disposed between the planar members. For example, if both top and bottom planar members are rigid and the separators are flexible, separators larger than the mean diameter will be compressed, and the planar members will approximate until more and more separators come into contact with the planar members, preventing further approximation. At that point, the height of the chamber approximates the average height of the separators and is readily ascertainable, provided the standard deviation of the separator heights is acceptable and the separators are sufficiently flexible. In another example, if the separators are rigid and the top planar member is flexible, the top planar member will deform and be "tented-up" in a small area around each of the larger separators and be lower over smaller separators. The chamber will have an average height which closely approximates average separator height, provided the top planar member is sufficiently flexible. [0014] An advantage of the present invention is, therefore, that a chamber is formed having a volume that is accurately determinable because the height of the chamber is substantially uniform. [0015] Another advantage of the present invention is that it can be manufactured in an inexpensive form and still provide the desired accuracy. The present invention does not require accurately machined voids or separators to accurately establish volume. Consequently, the invention can be manufactured inexpensively and still provide the desired accuracy. In addition, because it can be manufactured inexpensively, the present invention can practically be offered in a disposable form. [0016] These and other objects, features and advantages of the present invention will become apparent in light of the detailed description of the invention provided below, and as illustrated in the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0017] The principles of the invention are further clarified by referring to the following figures, where: [0018] FIG. 1 is a cross-sectional schematic of the invention of the prior art, using a system in which all elements are rigid; [0019] FIG. 2 is a cross-sectional schematic of the invention of the prior art, using a system in which all elements are rigid, and where particulate debris has been trapped; [0020] FIG. 3 is a cross-sectional schematic of the present invention, where the separators are flexible relative to the top and bottom planar members; [0021] FIG. 4 is a cross-sectional schematic of the present invention, where the top planar member is flexible in relation to all other elements; Continue reading... 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